Sadly no replies (wrong forum maybe? or just boring question..) so went ahead with water in vase. Losing vibrant colour quickly. Might have happened even faster with no water, who knows. Cheers anyway.

Drying seedheads works best when hung upside down for a while, till the stems harden. They won't hold that red color with any method. And the seeds may start to fall out in a year or so. They are pretty!

Thanks Susan, yes they lost the colour after several days. Pity they won't hold it but still worthwhile - similar to putting flowers in a vase. Wouldn't be the same if they stayed unchanging anyway..

Putting them in water when they're not growing will just make them rot. I also like the seedheads sculptural look. I'd pair them with a few sprigs of baby's breath.

I was hoping to prolong the red colour, but no. The dried out seed heads are good too though - I must try them in an arrangement like you suggest. Opium poppy seed pods are another interesting one.

Love the look of those echinacea seed heads, gotta do that for myself !!